It is known that brain neurotransmitters control behavior. The proposed research investigates a specific group of neurotransmitters, namely the catecholamines, that control eating behavior and appetite. Through a variety of brain manipulations, including cannula implants, lesions, knife cuts and neurotoxins, spontaneous and drug-induced behaviors are examined. The focus of these studies is on two catecholamine projection systems; and alpha-adrenergic system to the medial hypothalamus that stimulates eating and a beta-adrenergic and dopaminergic system to the lateral hypothalamus that inhibits eating. Through anatomical and histochemical studies, the neural substrates of these systems within the diencephalon and lower brainstem are being studied. The role of these systems in mediating psychotropic drug action is also being investigated. Furthermore, the precise function of these systems in regulating natural eating behavior and appetite for specific foods is being examined, through meal pattern analyses, dietary manipulations and chronic alterations in brain catecholamine activity. The relationship between brain catecholamines, glucocorticoids and eating behavior is also under investigation. The proposed efforts to examine brain catecholamine function and the central action of psychotropic drugs may establish an important foundation for understanding human eating disorders as well as unwanted side effects of drugs on appetite and body weight gain.